Bamboo microfiber three-dimensional network reinforced PBAT full-biodegradable polyester master batch

Abstract

This invention discloses a fully biodegradable PBAT masterbatch reinforced with a three-dimensional bamboo microfiber network. The masterbatch consists of a silane-epoxy dual-modified bamboo microfiber three-dimensional network reinforcing phase and a PBAT matrix phase, prepared via a three-step method of "steam explosion-high-speed shearing-in-situ self-assembly." The silane coupling agent and epoxy chain extender work synergistically to form covalent bonds on the surface of the bamboo microfibers, simultaneously inducing the bamboo microfibers to self-assemble into a continuous three-dimensional network structure during the melting process. The masterbatch exhibits a tensile strength of 28.5-35.2 MPa, an elastic modulus of 320-410 MPa, an elongation at break of 420-580%, and a water vapor permeability reduction of 35-45%. This invention solves the technical problems of weak interfacial bonding, limited improvement in mechanical properties, and easy agglomeration of bamboo fibers in traditional bamboo powder / PBAT composites. The preparation process is simple, can be mass-produced, and is suitable for applications such as agricultural films, packaging films, and disposable tableware.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable polymer materials technology, specifically relating to a bamboo microfiber three-dimensional network reinforced PBAT fully biodegradable polyester masterbatch. Background Technology

[0002] Polybutylene adipate (PBAT) is a high-performance, fully biodegradable polymer material with good toughness, ductility, and processability, and is widely used in packaging, agriculture, and disposable products. However, pure PBAT resin has drawbacks such as low modulus, insufficient strength, and high cost, which limit its further application.

[0003] Bamboo is a widely available, renewable, and biodegradable natural biomass material with advantages such as high specific strength and high specific modulus. Combining bamboo with PBAT to prepare biodegradable composite materials can not only reduce material costs but also improve the mechanical properties and rigidity of the composites. However, current technologies for combining bamboo with PBAT still have the following problems: 1. Most technologies use bamboo powder as a filler. However, bamboo powder has a large particle size and a small aspect ratio, so it can only play a filling role and cannot form an effective reinforcing network, resulting in limited improvement in mechanical properties.

[0004] 2. Bamboo fiber contains a large number of hydroxyl groups on its surface, making it highly hydrophilic. However, it has poor compatibility with the hydrophobic PBAT matrix, resulting in weak interfacial bonding and stress concentration, which reduces the toughness of the composite material.

[0005] 3. Bamboo fibers are prone to agglomeration during processing, making it difficult to disperse uniformly in the PBAT matrix and affecting the stability of the composite material's properties.

[0006] 4. Existing modification methods mostly use a single coupling agent, which has limited effect on interface modification and cannot achieve a balance between high strength and high toughness at the same time.

[0007] Therefore, developing a bamboo-based reinforced PBAT composite material that can form a continuous three-dimensional network structure in a PBAT matrix, has strong interfacial bonding and excellent mechanical properties has important theoretical significance and practical application value. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a fully biodegradable PBAT masterbatch reinforced with a bamboo microfiber three-dimensional network. This masterbatch is prepared using a three-step method of "steam explosion-high-speed shearing-in-situ self-assembly," forming a continuous bamboo microfiber three-dimensional network structure within the PBAT matrix. Simultaneously, a dual-interface modification system using silane coupling agents and epoxy chain extenders is employed to achieve a strong interfacial bond between bamboo microfibers and PBAT, solving the technical problems of weak interfacial bonding, limited improvement in mechanical properties, and easy agglomeration of bamboo fibers in traditional bamboo powder / PBAT composites.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A fully biodegradable PBAT polyester masterbatch reinforced with bamboo microfiber three-dimensional network is composed of a silane-epoxy dual-modified bamboo microfiber three-dimensional network reinforcing phase and a PBAT matrix phase, wherein the mass fraction of the silane-epoxy dual-modified bamboo microfiber three-dimensional network reinforcing phase is 15-40%, and the mass fraction of the PBAT matrix phase is 60-85%.

[0010] The preparation method of silane-epoxy dual-modified bamboo microfiber three-dimensional network reinforcement phase includes: cutting bamboo strips into 1-2 cm long segments, placing them in a steam explosion device, holding the pressure at 2.5-3.5 MPa for 120-180 seconds and then releasing the pressure instantly to obtain steam-exploded bamboo fibers; mixing the steam-exploded bamboo fibers with deionized water at a mass ratio of 1:15-1:20, and treating them in a high-speed shear disperser at a speed of 8000-12000 rpm for 30-60 minutes to obtain a bamboo microfiber suspension; filtering and washing the bamboo microfiber suspension until neutral, and drying it in a vacuum drying oven at 80-90℃ for 12-16 hours to obtain bamboo microfibers; mixing the bamboo microfibers with a silane coupling agent and an epoxy chain extender at a mass ratio of 100:2-5:1-3, and mixing them in a high-speed mixer at a speed of 1500-2000 rpm for 10-15 minutes to obtain silane-epoxy dual-modified bamboo microfibers.

[0011] The number average molecular weight of the PBAT matrix phase is 45,000-65,000, the melt index is 2.5-4.5 g / 10 min, and the test conditions are 190℃ and 2.16 kg. Before use, the PBAT matrix phase is dried in a vacuum drying oven at 80-85℃ for 8-12 hours, and the moisture content is controlled below 0.02%.

[0012] The silane coupling agent is γ-glycidyl etheroxypropyltrimethoxysilane, and its addition amount is 2-5% of the mass of bamboo microfiber.

[0013] The epoxy chain extender is a styrene-glycidyl methacrylate copolymer with an epoxy value of 0.8-1.2 mmol / g, and the amount added is 1-3% of the mass of bamboo microfiber.

[0014] The bamboo microfibers obtained by steam explosion treatment have a diameter of 200-800 nm, a length of 50-200 μm, and an aspect ratio of 100-500.

[0015] In the three-dimensional network structure formed by in-situ self-assembly, bamboo microfibers are interconnected through physical entanglement and chemical bonding, with a network node density of 1.2 × 10⁻⁶. 8 -3.5×10 8 pcs / cm³

[0016] γ-glycidyl etheroxypropyltrimethoxysilane undergoes a condensation reaction with the hydroxyl groups on the surface of bamboo microfiber to form Si-OC covalent bonds, with a reaction conversion rate of over 85%.

[0017] The epoxy groups of the styrene-glycidyl methacrylate copolymer undergo ring-opening reactions with the epoxy groups of the silane coupling agent and the terminal carboxyl groups of PBAT, forming interfacial covalent bonds that bridge the interface, increasing the interfacial bonding strength by more than 60%.

[0018] The masterbatch has a particle size of 2-4 mm, a bulk density of 0.65-0.75 g / cm³, and a moisture content of ≤0.05%.

[0019] The masterbatch achieves a biodegradation rate of over 90% within 180 days under composting conditions, meeting the requirements of GB / T19277.1-2025 standard.

[0020] The preparation method of the above-mentioned bamboo microfiber three-dimensional network reinforced PBAT fully biodegradable polyester masterbatch includes the following steps: 1. Steam explosion pretreatment: Cut bamboo strips into 1-2cm long sections, place them in a steam explosion device, introduce saturated steam, maintain pressure at 2.5-3.5MPa for 120-180 seconds, and then release the pressure instantly to obtain steam-exploded bamboo fiber.

[0021] 2. High-speed shear dispersion: Steam-exploded bamboo fiber and deionized water are mixed at a mass ratio of 1:15-1:20 and treated in a high-speed shear disperser at 8000-12000 rpm for 30-60 minutes to obtain a bamboo microfiber suspension; the bamboo microfiber suspension is filtered, washed until neutral, and dried in a vacuum drying oven at 80-90℃ for 12-16 hours to obtain bamboo microfiber.

[0022] 3. Dual-interface modification: Bamboo microfiber is mixed with γ-glycidyl etheroxypropyltrimethoxysilane and styrene-glycidyl methacrylate copolymer at a mass ratio of 100:2-5:1-3 and mixed in a high-speed mixer at a speed of 1500-2000 rpm for 10-15 minutes to obtain silane-epoxy dual-modified bamboo microfiber.

[0023] 4. Melt extrusion granulation: Silane-epoxy dual-modified bamboo microfiber and dried PBAT are mixed evenly at a mass ratio of 15-40:60-85, added to a twin-screw extruder, and melt-extruded at a temperature of 145-165℃ with a screw speed of 180-250rpm. After water cooling, pelletizing and drying, bamboo microfiber three-dimensional network reinforced PBAT fully biodegradable polyester masterbatch is obtained.

[0024] The beneficial effects of this invention are as follows: 1. This invention utilizes steam explosion combined with high-speed shearing technology to prepare bamboo microfibers. By precisely controlling the steam explosion pressure to 2.5-3.5 MPa, the holding time to 120-180 seconds, and the high-speed shearing speed to 8000-12000 rpm and the processing time to 30-60 minutes, bamboo microfibers with diameters of 200-800 nm, lengths of 50-200 μm, and aspect ratios of 100-500 are prepared. These bamboo microfibers possess a large specific surface area and high surface activity, providing a foundation for the formation of a three-dimensional network structure.

[0025] 2. This invention utilizes an in-situ self-assembly process to enable silane-epoxy dual-modified bamboo microfibers to self-assemble under twin-screw extrusion conditions of 145-165℃ and 180-250rpm, forming a node density of 1.2×10⁻⁶ through physical entanglement and chemical bonding. 8 -3.5×10 8 A continuous three-dimensional network structure with [number] cells / cm³. This structure can effectively transfer stress and significantly improve the tensile strength and elastic modulus of the composite material.

[0026] 3. This invention employs a dual-interface modification system using a silane coupling agent and an epoxy chain extender. γ-glycidyl etheroxypropyltrimethoxysilane forms Si-OC covalent bonds with the hydroxyl groups on the surface of bamboo microfiber, achieving a reaction conversion rate of over 85%. Simultaneously, the epoxy groups of the styrene-glycidyl methacrylate copolymer undergo ring-opening reactions with the epoxy groups of the silane coupling agent and the terminal carboxyl groups of PBAT, forming a quaternary covalent bond bridge of "bamboo microfiber-silane-epoxy-PBAT," increasing the interfacial bonding strength by over 60%. The synergistic effect of these two methods achieves a strong interfacial bond between bamboo microfiber and the PBAT matrix.

[0027] 4. The bamboo microfiber three-dimensional network reinforced PBAT fully biodegradable polyester masterbatch prepared by this invention has a tensile strength of 28.5-35.2 MPa, an elastic modulus of 320-410 MPa, an elongation at break of 420-580%, and a water vapor transmission coefficient reduced by 35-45%, achieving a balance of high strength, high modulus, and high toughness.

[0028] 5. The preparation process of this invention is simple, and it can be mass-produced on existing twin-screw extrusion equipment. The production cost is low, the product is completely biodegradable, environmentally friendly, and suitable for fields such as mulch film, packaging film, and disposable tableware. Attached Figure Description

[0029] Figure 1 This is a diagram of the four-level covalent bond bridging of the present invention. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to specific embodiments. Example 1

[0031] 1. Steam explosion pretreatment: Cut bamboo strips into 1-2cm long sections, place them in a steam explosion device, introduce saturated steam, maintain pressure at 3.0MPa for 150 seconds, and then release the pressure instantly to obtain steam-exploded bamboo fiber.

[0032] 2. High-speed shear dispersion: Steam-exploded bamboo fiber and deionized water were mixed at a mass ratio of 1:18 and treated in a high-speed shear disperser at 10,000 rpm for 45 minutes to obtain a bamboo microfiber suspension. The bamboo microfiber suspension was filtered, washed until neutral, and dried in a vacuum drying oven at 85℃ for 14 hours to obtain bamboo microfiber. Testing showed that the bamboo microfiber had a diameter of 300-600 nm, a length of 80-150 μm, and an aspect ratio of 200-400.

[0033] 3. Dual-interface modification: 100 kg of bamboo microfiber was mixed with 3 kg of γ-glycidyl etheroxypropyltrimethoxysilane and 2 kg of styrene-glycidyl methacrylate copolymer. The mixture was then mixed in a high-speed mixer at 1800 rpm for 12 minutes to obtain silane-epoxy dual-modified bamboo microfiber.

[0034] 4. Melt Extrusion Granulation: 25 kg of silane-epoxy dual-modified bamboo microfiber was mixed evenly with 75 kg of dried PBAT and added to a twin-screw extruder. The temperatures of each section of the twin-screw extruder were 145℃, 150℃, 155℃, 160℃, 160℃, 155℃, and 150℃, respectively, and the screw speed was 220 rpm. After water cooling, pelletizing, and drying, a fully biodegradable polyester masterbatch of bamboo microfiber three-dimensional network reinforced PBAT was obtained. Testing showed that the masterbatch particle size was 2.5-3.5 mm, the bulk density was 0.70 g / cm³, and the moisture content was 0.03%. Example 2

[0035] 1. Steam explosion pretreatment: Cut bamboo strips into 1-2cm long sections, place them in a steam explosion device, introduce saturated steam, maintain pressure at 2.5MPa for 180 seconds, and then release the pressure instantly to obtain steam-exploded bamboo fiber.

[0036] 2. High-speed shear dispersion: Steam-exploded bamboo fiber and deionized water were mixed at a mass ratio of 1:15 and treated in a high-speed shear disperser at 8000 rpm for 60 minutes to obtain a bamboo microfiber suspension. The bamboo microfiber suspension was filtered, washed until neutral, and dried in a vacuum drying oven at 80℃ for 16 hours to obtain bamboo microfiber. Testing showed that the bamboo microfiber had a diameter of 400-800 nm, a length of 100-200 μm, and an aspect ratio of 150-350.

[0037] 3. Dual-interface modification: 100 kg of bamboo microfiber was mixed with 2 kg of γ-glycidyl etheroxypropyltrimethoxysilane and 1 kg of styrene-glycidyl methacrylate copolymer. The mixture was then mixed in a high-speed mixer at 1500 rpm for 15 minutes to obtain silane-epoxy dual-modified bamboo microfiber.

[0038] 4. Melt Extrusion Granulation: 15 kg of silane-epoxy dual-modified bamboo microfiber was mixed evenly with 85 kg of dried PBAT and added to a twin-screw extruder. The temperatures of each section of the twin-screw extruder were 145℃, 150℃, 155℃, 160℃, 160℃, 155℃, and 150℃, respectively, and the screw speed was 180 rpm. After water cooling, pelletizing, and drying, a fully biodegradable polyester masterbatch of bamboo microfiber three-dimensional network reinforced PBAT was obtained. Testing showed that the masterbatch particle size was 2.0-3.0 mm, the bulk density was 0.67 g / cm³, and the moisture content was 0.04%. Example 3

[0039] 1. Steam explosion pretreatment: Cut bamboo strips into 1-2cm long sections, place them in a steam explosion device, introduce saturated steam, maintain pressure at 3.5MPa for 120 seconds, and then release the pressure instantly to obtain steam-exploded bamboo fiber.

[0040] 2. High-speed shear dispersion: Steam-exploded bamboo fiber and deionized water were mixed at a mass ratio of 1:20 and treated in a high-speed shear disperser at 12,000 rpm for 30 minutes to obtain a bamboo microfiber suspension. The bamboo microfiber suspension was filtered, washed until neutral, and dried in a vacuum drying oven at 90℃ for 12 hours to obtain bamboo microfiber. Testing showed that the bamboo microfiber had a diameter of 200-500 nm, a length of 50-120 μm, and an aspect ratio of 250-500.

[0041] 3. Dual-interface modification: 100 kg of bamboo microfiber was mixed with 5 kg of γ-glycidyl etheroxypropyltrimethoxysilane and 3 kg of styrene-glycidyl methacrylate copolymer. The mixture was then mixed in a high-speed mixer at 2000 rpm for 10 minutes to obtain silane-epoxy dual-modified bamboo microfiber.

[0042] 4. Melt Extrusion Granulation: 40 kg of silane-epoxy dual-modified bamboo microfiber was mixed evenly with 60 kg of dried PBAT and added to a twin-screw extruder. The temperatures of each section of the twin-screw extruder were 145℃, 150℃, 155℃, 165℃, 165℃, 155℃, and 150℃, respectively, and the screw speed was 250 rpm. After water cooling, pelletizing, and drying, a fully biodegradable polyester masterbatch of bamboo microfiber three-dimensional network reinforced PBAT was obtained. Testing showed that the masterbatch particle size was 3.0-4.0 mm, the bulk density was 0.73 g / cm³, and the moisture content was 0.02%.

[0043] Comparative Example 1 The difference between this comparative example and Example 1 is that, instead of steam explosion pretreatment, the bamboo chips were directly pulverized into 200-mesh bamboo powder before subsequent processing. The specific steps are as follows: 1. Crush the bamboo strips into 200-mesh bamboo powder and dry them in a vacuum drying oven at 85℃ for 14 hours.

[0044] 2. Mix 100 kg of bamboo powder with 3 kg of γ-glycidyl etheroxypropyltrimethoxysilane and 2 kg of styrene-glycidyl methacrylate copolymer, and mix in a high-speed mixer at 1800 rpm for 12 minutes to obtain modified bamboo powder.

[0045] 3. Mix 25 kg of modified bamboo powder with 75 kg of dried PBAT evenly, and add it to a twin-screw extruder. The temperatures of each section of the twin-screw extruder are 145℃, 150℃, 155℃, 160℃, 160℃, 155℃, and 150℃, respectively, and the screw speed is 220 rpm. After water cooling, pelletizing, and drying, bamboo powder reinforced PBAT masterbatch is obtained.

[0046] Comparative Example 2 The difference between this comparative example and Example 1 is that no dual-interface modification was performed; only γ-glycidoxypropyltrimethoxysilane was used for single modification. The specific steps are as follows: 1. Steam explosion pretreatment: Same as in Example 1.

[0047] 2. High-speed shear dispersion: Same as in Example 1.

[0048] 3. Single interface modification: 100 kg of bamboo microfiber was mixed with 3 kg of γ-glycidyl etheroxypropyltrimethoxysilane and mixed in a high-speed mixer at 1800 rpm for 12 minutes to obtain silane-modified bamboo microfiber.

[0049] 4. Melt extrusion granulation: Mix 25 kg of silane-modified bamboo microfiber with 75 kg of dried PBAT evenly, and add it to a twin-screw extruder. The temperatures of each section of the twin-screw extruder are 145℃, 150℃, 155℃, 160℃, 160℃, 155℃, and 150℃, respectively, and the screw speed is 220 rpm. After water cooling, pelletizing, and drying, bamboo microfiber reinforced PBAT masterbatch is obtained.

[0050] Comparative Example 3 The difference between this comparative example and Example 1 is that no dual-interface modification was performed; only a single modification was performed using a styrene-glycidyl methacrylate copolymer. The specific steps are as follows: 1. Steam explosion pretreatment: Same as in Example 1.

[0051] 2. High-speed shear dispersion: Same as in Example 1.

[0052] 3. Single interface modification: 100 kg of bamboo microfiber was mixed with 2 kg of styrene-glycidyl methacrylate copolymer and mixed in a high-speed mixer at 1800 rpm for 12 minutes to obtain epoxy-modified bamboo microfiber.

[0053] 4. Melt extrusion granulation: Mix 25 kg of epoxy-modified bamboo microfiber with 75 kg of dried PBAT evenly and add it to a twin-screw extruder. The temperatures of each section of the twin-screw extruder are 145℃, 150℃, 155℃, 160℃, 160℃, 155℃, and 150℃, respectively, and the screw speed is 220 rpm. After water cooling, pelletizing, and drying, bamboo microfiber reinforced PBAT masterbatch is obtained.

[0054] Comparative Example 4 The difference between this comparative example and Example 1 is that steam explosion and high-speed shearing treatment are not performed; commercially available bamboo fiber is used directly. The specific steps are as follows: 1. Dry commercially available bamboo fiber (diameter 10-20μm, length 1-2mm) in a vacuum drying oven at 85℃ for 14 hours.

[0055] 2. Mix 100 kg of commercially available bamboo fiber with 3 kg of γ-glycidyl etheroxypropyltrimethoxysilane and 2 kg of styrene-glycidyl methacrylate copolymer, and mix in a high-speed mixer at 1800 rpm for 12 minutes to obtain modified bamboo fiber.

[0056] 3. Mix 25 kg of modified bamboo fiber with 75 kg of dried PBAT evenly, and add it to a twin-screw extruder. The temperatures of each section of the twin-screw extruder are 145℃, 150℃, 155℃, 160℃, 160℃, 155℃, and 150℃, respectively, and the screw speed is 220 rpm. After water cooling, pelletizing, and drying, bamboo fiber reinforced PBAT masterbatch is obtained.

[0057] Comparative Example 5 This comparative example uses pure PBAT masterbatch, prepared as follows: PBAT was dried in a vacuum drying oven at 85℃ for 14 hours and then fed into a twin-screw extruder. The temperatures of each section of the twin-screw extruder were 145℃, 150℃, 155℃, 160℃, 160℃, 155℃, and 150℃, respectively, and the screw speed was 220 rpm. After water cooling, pelletizing, and drying, pure PBAT masterbatch was obtained.

[0058] Performance testing The masterbatches prepared in Examples 1-3 and Comparative Examples 1-5 were dried in a vacuum drying oven at 80°C for 8 hours, and then injection molded into standard test specimens at an injection molding machine with an injection temperature of 150-165°C. Performance testing was conducted according to the following standards: 1. Tensile properties: Tested according to GB / T1040.2-2022 standard, the tensile rate is 50 mm / min.

[0059] 2. Impact performance: Tested according to GB / T1043.1-2008 standard using a simply supported beam impact testing machine, without notches.

[0060] 3. Water vapor transmission coefficient: Tested according to GB / T1037-2021 standard, with test conditions of 38℃ and relative humidity of 90%.

[0061] 4. Biodegradation rate: Tested according to GB / T19277.1-2025 standard, with a test period of 180 days.

[0062] 5. Masterbatch particle size: Tested according to GB / T6003.1-2022 standard.

[0063] 6. Bulk density: Tested according to GB / T1636-2008 standard.

[0064] 7. Moisture content: Tested according to GB / T6284-2006 standard.

[0065] The test results are shown in Table 1.

[0066] Table 1. Performance test results of the examples and comparative examples. sample Tensile strength (MPa) Elastic modulus (MPa) Elongation at break (%) Unnotched impact strength of a simply supported beam (kJ / m²) Water vapor transmission coefficient (g·cm / (cm²·s·Pa)) 180-day biodegradation rate (%) Masterbatch particle size (mm) Bulk density (g / cm³) Moisture content (%) Example 1 32.6 375 510 48.2 <![CDATA[2.15×10 -12 ]]> 92.3 2.5-3.5 0.70 0.03 Example 2 28.5 320 580 52.7 <![CDATA[2.48×10 -12 ]]> 93.5 2.0-3.0 0.67 0.04 Example 3 35.2 410 420 43.5 <![CDATA[1.89×10 -12 ]]> 90.8 3.0-4.0 0.73 0.02 Comparative Example 1 19.8 210 280 25.6 <![CDATA[3.32×10 -12 ]]> 89.7 2.5-3.5 0.68 0.03 Comparative Example 2 24.3 285 390 36.8 <![CDATA[2.76×10 -12 ²]]> 91.5 2.5-3.5 0.69 0.03 Comparative Example 3 22.7 260 350 32.4 <![CDATA[2.91×10 -12 ]]> 91.2 2.5-3.5 0.69 0.03 Comparative Example 4 21.5 235 320 28.9 <![CDATA[3.15×10 -12 ]]> 90.4 2.5-3.5 0.68 0.03 Comparative Example 5 18.2 165 650 56.3 <![CDATA[3.87×10 -12 ]]> 95.1 2.5-3.5 0.65 0.02 As can be seen from Table 1: 1. The bamboo microfiber three-dimensional network reinforced PBAT fully biodegradable polyester masterbatches prepared in Examples 1-3 exhibited significantly higher tensile strength, elastic modulus, and impact strength than those in Comparative Examples 1-4, while maintaining a high elongation at break. Among them, Example 1 showed the best overall performance, with a tensile strength of 32.6 MPa, an elastic modulus of 375 MPa, an elongation at break of 510%, and an unnotched impact strength of 48.2 kJ / m².

[0067] 2. Compared with Comparative Example 1, the tensile strength of Example 1 increased by 64.6%, the elastic modulus increased by 78.6%, the elongation at break increased by 82.1%, the unnotched impact strength of the simply supported beam increased by 88.3%, and the water vapor transmission coefficient decreased by 35.2%. This indicates that bamboo microfibers prepared by steam explosion combined with high-speed shearing can form an effective three-dimensional network reinforcement structure, significantly improving the mechanical properties and barrier properties of the composite material.

[0068] 3. Compared with Comparative Examples 2 and 3, the tensile strength of Example 1 increased by 34.2% and 43.6%, respectively; the elastic modulus increased by 31.6% and 44.2%, respectively; and the unnotched impact strength of the simply supported beam increased by 31.0% and 48.8%, respectively. This indicates that the dual-interface modification system of silane coupling agent and epoxy chain extender has a synergistic effect and can significantly improve the interfacial bonding strength between bamboo microfiber and PBAT matrix.

[0069] 4. Compared with Comparative Example 4, the tensile strength of Example 1 increased by 51.6%, the elastic modulus increased by 59.6%, the elongation at break increased by 59.4%, and the unnotched impact strength of the simply supported beam increased by 66.8%. This indicates that the bamboo microfiber prepared by this invention has a better reinforcing effect than commercially available bamboo fiber.

[0070] 5. Compared with Comparative Example 5, Example 1 showed a 79.1% increase in tensile strength, a 127.3% increase in elastic modulus, a 44.4% decrease in water vapor transmission coefficient, and maintained an elongation at break of 510%, achieving a balance of high strength, high modulus, and high toughness.

[0071] 6. All samples achieved a biodegradability rate of over 90% after 180 days, meeting the requirements for fully biodegradable materials.

[0072] 7. The masterbatches prepared in Examples 1-3 all have a particle size in the range of 2-4 mm, a bulk density in the range of 0.65-0.75 g / cm³, and a moisture content of ≤0.05%, which meet the quality requirements of masterbatch products.

[0073] Core structure formation mechanism and performance correlation 1. The formation process of continuous three-dimensional networks The three-step method of "steam explosion-high-speed shearing-in-situ self-assembly" in this invention is the key to network structure formation: Steam explosion (3.0 MPa, 150 s) exfoliates high aspect ratio nanoscale bamboo microfibers, giving the fibers self-entanglement ability; High-speed shearing (10,000 rpm, 45 min) achieves uniform dispersion of individual fibers, avoiding agglomeration; During melt extrusion, the double-modified bamboo microfibers spontaneously overlap under shear force and intermolecular forces, forming a stable continuous three-dimensional network through physical entanglement and chemical bonding.

[0074] 2. Strong binding effect of dual-interface modification Figure 1 The 8-12nm thick transition layer is a direct manifestation of the quaternary covalent bond bridging of "bamboo microfiber-silane-epoxy-PBAT": γ-glycidyl etheroxypropyltrimethoxysilane forms Si-OC covalent bonds with the hydroxyl groups on the surface of bamboo microfiber (reaction conversion rate of over 85%). The epoxy groups of the styrene-glycidyl methacrylate copolymer undergo ring-opening reactions with the epoxy groups of silane and the terminal carboxyl groups of PBAT, forming a continuous covalent bond interface, which increases the interfacial bonding strength by more than 60%.

[0075] 3. Table 2 Structure-Performance Correspondence Structural features Corresponding performance improvement Measured data (Example 1) Global Continuous 3D Network Skeleton Efficient stress transfer enhances strength and modulus. Tensile strength 32.6 MPa (79.1% higher than pure PBAT), elastic modulus 375 MPa (+127.3%) Covalent bond interface layer Avoid interface debonding and retain high toughness Elongation at break: 510%; Impact strength of simply supported beam: 48.2 kJ / m² Twisted 3D mesh path Extend the water vapor diffusion path and improve barrier properties <![CDATA[Water vapor transmission coefficient 2.15×10 -12 g·cm / (cm²·s·Pa) (compared with pure PBAT - 44.4%)]]> biodegradable components Maintain biodegradability The compost degradation rate is 92.3% after 180 days. Structural differences from traditional composite materials The three-dimensional network structure of this invention is fundamentally different from existing technologies: Comparative Example 1 (Bamboo Powder Reinforcement): The bamboo powder is dispersed as isolated particles without a continuous network, and only serves as a filler, resulting in limited improvement in mechanical properties; Compared with control sample 2 / 3 (single modification): the interface bonding is weak, the network nodes are only physically entangled, they are easily disintegrated under stress, and the toughness is significantly reduced; Comparative Example 4 (commercially available bamboo fiber): The fiber diameter is large (10-20μm) and the aspect ratio is small, which makes it impossible to form an effective nano-network and results in poor reinforcement.

[0076] The above results show that the bamboo microfiber three-dimensional network reinforced PBAT fully biodegradable polyester masterbatch prepared by the three-step method of "steam explosion-high-speed shearing-in-situ self-assembly" in this invention has successfully solved the technical problems of weak interfacial bonding, limited improvement of mechanical properties, and easy agglomeration of bamboo powder / PBAT composite materials in traditional bamboo powder / PBAT composite materials. It has excellent comprehensive performance and broad application prospects.

Claims

1. A bamboo microfiber three-dimensional network reinforced PBAT fully biodegradable polyester masterbatch, characterized in that, The formulation consists of a silane-epoxy dual-modified bamboo microfiber three-dimensional network reinforcement phase A and a PBAT matrix phase B, wherein the mass fraction of A is 15-40% and the mass fraction of B is 60-85%. The A is prepared by the following method: bamboo strips are subjected to steam explosion treatment at 2.5-3.5 MPa pressure for 120-180 seconds to obtain bamboo microfibers, and then the bamboo microfibers are mixed and modified with γ-glycidyl etheroxypropyltrimethoxysilane and styrene-glycidyl methacrylate copolymer at a mass ratio of 100:2-5:1-3. The A is in-situ self-assembled with B to form a continuous three-dimensional network structure during the twin-screw melt extrusion at 145-165℃, screw rotation speed 180-250rpm, the three-dimensional network is connected by physical entanglement and chemical bonding between the bamboo microfibers, the network node density is 1.2×10 8 -3.5×10 8 -3.5×10 2. The bamboo microfiber three-dimensional network reinforced PBAT fully biodegradable polyester masterbatch according to claim 1, characterized in that, The preparation method of silane-epoxy dual-modified bamboo microfiber three-dimensional network reinforcement phase A includes: cutting bamboo strips into 1-2 cm long segments, placing them in a steam explosion device, holding the pressure at 2.5-3.5 MPa for 120-180 seconds and then releasing the pressure instantly to obtain steam-exploded bamboo fibers; mixing the steam-exploded bamboo fibers with deionized water at a mass ratio of 1:15-1:20, and treating them in a high-speed shear disperser at a speed of 8000-12000 rpm for 30-60 minutes to obtain a bamboo microfiber suspension; filtering and washing the bamboo microfiber suspension until neutral, and drying it in a vacuum drying oven at 80-90℃ for 12-16 hours to obtain bamboo microfibers; mixing the bamboo microfibers with a silane coupling agent and an epoxy chain extender at a mass ratio of 100:2-5:1-3, and mixing them in a high-speed mixer at a speed of 1500-2000 rpm for 10-15 minutes to obtain silane-epoxy dual-modified bamboo microfibers.

3. The bamboo microfiber three-dimensional network reinforced PBAT fully biodegradable polyester masterbatch according to claim 1, characterized in that, The number average molecular weight of PBAT matrix phase B is 45,000-65,000, the melt index is 2.5-4.5 g / 10 min, and the test conditions are 190℃ and 2.16 kg. Before use, PBAT matrix phase B is dried in a vacuum drying oven at 80-85℃ for 8-12 hours, and the moisture content is controlled below 0.02%.

4. The bamboo microfiber three-dimensional network reinforced PBAT fully biodegradable polyester masterbatch according to claim 2, characterized in that, The amount of γ-glycidyl etheroxypropyltrimethoxysilane added is 2-5% of the mass of bamboo microfiber.

5. The bamboo microfiber three-dimensional network reinforced PBAT fully biodegradable polyester masterbatch according to claim 2, characterized in that, The styrene-glycidyl methacrylate copolymer has an epoxy value of 0.8-1.2 mmol / g and is added at 1-3% of the mass of bamboo microfiber.

6. The bamboo microfiber three-dimensional network reinforced PBAT fully biodegradable polyester masterbatch according to claim 1, characterized in that, The bamboo microfibers obtained by steam explosion treatment have a diameter of 200-800 nm, a length of 50-200 μm, and an aspect ratio of 100-500.

7. The bamboo microfiber three-dimensional network reinforced PBAT fully biodegradable polyester masterbatch according to claim 4, characterized in that, γ-glycidyl etheroxypropyltrimethoxysilane undergoes a condensation reaction with the hydroxyl groups on the surface of bamboo microfiber to form Si-OC covalent bonds, with a reaction conversion rate of over 85%.

8. The bamboo microfiber three-dimensional network reinforced PBAT fully biodegradable polyester masterbatch according to claim 5, characterized in that, The epoxy groups of the styrene-glycidyl methacrylate copolymer undergo ring-opening reactions with the epoxy groups of the silane coupling agent and the terminal carboxyl groups of PBAT, forming interfacial covalent bonds that bridge the interface, increasing the interfacial bonding strength by more than 60%.

9. The bamboo microfiber three-dimensional network reinforced PBAT fully biodegradable polyester masterbatch according to claim 1, characterized in that, The masterbatch has a particle size of 2-4 mm, a bulk density of 0.65-0.75 g / cm³, and a moisture content of ≤0.05%.

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